This weekend marks the end of 2013's daylight-saving time. We set back our clocks one hour at 2 a.m. on Sunday, Nov. 3.

Although our mornings will be brighter, most Americans will now start to leave work in total darkness, ushering in the annual era of SAD, or seasonal affected disorder, a form of clinical depression that affects about 5 percent of the U.S. population. Even if you don't have full-blown SAD, you can experience the "winter blues," or feelings of exhaustion, sluggishness and sadness, Michael Terman, Ph.D., the author of the new book Reset Your Inner Clock and a professor of psychiatry at Columbia University, told Weather.com.

(ABOVE: 18 Ways Sleep Deprivation Hurts Your Body and Mind)

"When we suddenly switch the hands of the clock, it confuses our inner clock, which has been adjusted to synchronize with day-night cycle," he explained. "This can cause problems with sleep, mood, digestive function and mental alertness that can last for days and even weeks in some people."

As we progress further into winter, our bodies become even less in-sync with the sun, which can affect the brain's release of melatonin, the sleep hormone. As the sunrise happens later and later throughout the season, the brain secretes melatonin later into the morning, causing daytime sleepiness and sluggishness.

This effect is particularly pronounced among night owls — the portion of the population that naturally releases melatonin beginning later at night and then later into the morning. (So if you like to stay up late and then sleep in, it's because of your brain's natural chemistry — just explain that to your boss.)

The fix, Dr. Terman details in his book, is light therapy, or light boxes applied at a certain time in the morning to stop the production of melatonin and wake up the inner clock. "Light therapy works quickly for most people," he said. "Within several days or a week the sluggishness or depression of winter is greatly reduced."

But you can't just buy a light box and turn it on whenever you want to wake up in the morning, he said. The best time for light therapy can vary greatly from person to person. "If you take the light too early relative to your internal night you can make the problem worse," he said. Dr. Terman and his colleagues at the Center for Environmental Therapeutics created a sleep preference quiz that can fairly accurately estimate a person's melatonin patterns — and help patients time light therapy accordingly. (It's available here.)

One last word of caution from Dr. Terman: You can't fight wintertime sluggishness by sleeping more or sleeping in on the weekends. Those morning hours of sunlight are exactly what you need to fight the winter blues, he said. "Sleeping in on the weekends only increases the severity of winter depression," he said. "If you're staying in the dark during the morning hours, your inner clock is slipping later out of sync."